This project is designed to provide information about the organization of neuronal systems in the mammalian spinal cord that are involved in the neural control of movement. There are three current sub-projects: 1) studies of synaptic transmission; 2) studies of the neural circuits that produce coordinated locomotion in a primitive amphibian; and 3) studies of the quantitative morphology of motoneurons in the neonatal mouse spinal cord. All of these studies use in vitro preparations of brain stem slices or isolated en bloc spinal cord of neonatal mice or amphibians. [unreadable] [unreadable] We have completed an extensive analysis of data from 17 fully-reconstructed lumbosacral motoneurons in the same two age groups (P2-4 nd P10-12) of neonatal mice that were obtained during the above electrophysiological experiments. The analysis was done in collaboration with Dr. Giorgio Ascoli at the Krasnow Institute of George Mason University. Despite considerable growth in overall size, especially dendritic length, motoneurons in the two age groups showed little change in the branching structure (topology) of their dendritic trees. A full report has been published in the Journal of Comparative Neurology.